Research On Effect Of Modified Semi Conductive Material On The Space Charge Behaviour In XLPE

HVDC transmission technology has the advantages of high capacity, long distance, high operational stability, low loss and the ability to connect asynchronous power grids. With the increasingly maturing of the flexible HVDC transmission technology, the application of XLPE insulated HVDC cables has rapidly increased. One of the main defects of XLPE insulation is that the space charge injection is serious. Theoretical study shows that: The injection of space charge into the XLPE insulation layer can be restrained by modifying the semi conductive shielding layer and the interface of semi conductive shield/XLPE. Currently, the production and price of semi-conductive shielding materials for HVDC cables are mainly dominated by some multinational corporations. So research on the influence of modification of semi conductive shielding material on the space charge distribution in XLPE insulation can provide theoretical guidance for the development of high-performance products and has both academic significance and engineering application value.In this paper, the semi-conductive composite materials are prepared by the melt blending process using low density polyethylene（LDPE） andethylene-ethyl acrylate copolymer（EEA） as matrix resin, carbon black（CB） as the conductive filler, BIPB as the crosslinking agent. The conductivity, mechanical properties, rheological properties and the ability to suppress the space charge of each composite material and the effects of different types and content of CB, nano-materials and electrode polarity on space charge are tested. The research results show that: With the increase of CB content, the mass resistivity, the tensile strength, the elongation at break and the melt flow rate（MFR） is gradually decreasing. The amount of space charge injection is reduced and the inhibition ability of space charge injection is enhanced. The higher structure, the smaller particle size, the larger specific surface area of carbon black（CB） is, the stronger the ability of semi conductive shielding materials to suppress the space charge to the XLPE insulation is. Adding appropriate amount of nano MgO, nano Al₂O₃, nano SiC to semi conductive shielding materials can improve the inhibition ability of space charge injection of semi conductive shielding material.